No it converts the carbon into heat / energy. No carbon is left.

The extra fuel is injected into the cylinder head. If the fuel is not metered correctly some can end up getting past the scraper ring. Volvo changed the metering and monitoring and the scraper rings some years ago so it's not an issue nowadays unless the engine has a fault.

So if I understand that correctly the fuel is injected via the existing injectors that handle the usual fuelling & regeneration is basically over-fuelling to raise the temperature of the DPF?

Basically yeah altho it is more of a multi inject process rather than a full fuel dump in one go

Volvo fit their DPF's very close to the engine so they run hot enough to burn the fuel and carbon deposits together. Other manufacturers who can't fit the DPF close enough to the engine use Ad Blue to lower the necessary burn temperature.

Increasing the tension on the rings does result in increased wear of both the ring and cylinder.

If you inject extra fuel into the cylinder head some of it will get past the rings and valve guides into the oil. Normal diesel evapourates from hot engine oil, BUT the Bio content does not, so it accumulates and is real bad news in terms of thinning the oil and interferring with the action of the anti wear additives.

When the engine block and injector tips are in perfect condition the amount of fuel in the oil might be less than the 2% listed by an oil analysis lab for a warning flag, but in many cases of older cars or those doing a lot of short trips the amount of fuel will be about that limit, particularly if the injectors are gummed up from using supermarket fuel.

The solution: Cut the oil change interval to half the Max recommended (No need to change the oil filter until max interval) and use a direct feed injection cleaner like Liqui Moly Diesel Purge to fill up the fuel filter housing when the element is changed. A can of a major brand diesel fuel additive every OCI will also work to some extent.

Volvo list 0w30 as the oil spec for newer engines, BUT if your engine is worn or subject to fuel contamination, increase it to an 0 or 5w40 full synthetic.

It has nothing to do with bad fuel metering , just the biofuel fysics and the relatively long time the (big biodiesel droplets)fuel spends in the exhauststroke and not burning.
If the fuel was badly metered than the the dpf temp would be too hot or cold .
The dpf temp is pretty good managed , the best option tho is an extra fuelinjector in the catalyst . but thats a money issue.

Its no coincedence that the countries with high biodieselcontent (7% or more) have these risingoilevel issues and the countries that run on 2% or less have pretty non existent rising oillevels

The UK has had 7% bio content for many years. Volvo fixed the issue years ago. If you look at the date of the thread start it was 2010.

Roy

I think the biofuel content was at least 7% and even over 10% in some cases (in the past)
I have both ecu maps with and without the dpf software update and they seem to run under the same lamdas during regeneration (including post injection) also the regeneration intervals are the same
I had no rising oilevels with both of them but biocontent is max 2% over here

Now with more modern dieselengines nowadays with piezo injectors there are more injections pro cycle possible so maybe that curbs a bit
And if the oilring is different (source?} than it could a be bit of a difference
But with the older dpf d5ś it was almost the german and uk d5ś with the high biodiesel content that had the excessive problems

I read every post on the XC90 D5 forum and there never was a UK XC90 D5 with a rising oil level. There was one very early Spanish one that Volvo replaced the engine for a new one and took the old one back to the factory to experiment on, but that was it for the UK XC90 forum.

There was an issue with some of the 60 series D5's, but as I said the issue was sorted ages ago and there have been no issues recently that I've seen.

UK diesel has been 7% bio for about 11 years. Was 5% before that.

Roy